Storage Virtualization Kh. Rashedul Arefin Outlines • Types of Storage • Accessing Data • Storage Area Network (SAN) • Storage Virtualization Types of Storage • Primary Storage – Volatile storage that directly accessible by Computer’s CPU – Small Capacity – Very Fast • Secondary Storage – Nonvolatile – Not directly accessible by CPU – Require I/O channel – Slower • Tertiary Storage – Removable mass storage – Slower than other two types – Lower Cost Accessing Data • Block Based Access – SCSI – Mainframe Storage Access – Advanced Technology Attachment (ATA) • File Access – Network Access Protocol (NAS) – Network File System (NFS) – Common Internet File System (CIFS) • Record Access – Open DataBase Connectivity (ODBC) – Java DataBase Connectivity (JDBC) – Structured Query Language (SQL) Chapter 8: Block Storage Technologies 239 ■ Arbitrated loop: Permits up to 127 devices to communicate with each other in a looped connection. Fibre Channel hubs were designed to improve reliability in these topolo- gies, but with the higher adoption of switched fabrics, Fibre Channel loop interfaces are more likely to be found on legacy storage devices such as JBODs or older tape libraries. ■ Switched fabric: Comprises Fibre Channel devices that exchange data through Fibre ChannelStorage switches and theoretically Area supports up Network to 16 million devices in a single (SAN) fabric. Figure 8-16 illustrates these topologies, where each arrow represents a single fiber connection. NL_Port NL_Port N_Port N_Port N_Port NL_Port NL_Port F_Port FL_Port Switch NL_Port E_Port E_Port Switch NL_Port NL_Port NL_Port F_Port Hub NL_Port NL_Port NL_Port NL_Port Arbitrated LoopPoint-to-Point Switched Fabric ptg17120290 Figure 8-16 Fibre Channel Topologies N_PortFigure 8-16: alsoNode introduces Port the following Fibre ChannelF_Port port: Fabrictypes: Port 8 E_Port: Expansion Port NL_Port■ Node Port: (N_Port):Node LoopInterface Porton a Fibre ChannelFL_Port end host: Fabricin a point-to-point Loop or(Public) Port (Create ISL) switched fabric topology. ■ Node Loop Port (NL_Port): Interface that is installed in a Fibre Channel end host to allow connections through an arbitrated loop topology. ■ Fabric Port (F_Port): Interface Fibre Channel switch that is connected to an N_Port. ■ Fabric Loop Port (FL_Port): Fibre Channel switch interface that is connected to a public loop. A fabric can have multiple FL_Ports connected to public loops, but, per definition, a private loop does not have a fabric connection. ■ Expansion Port (E_Port): Interface that connects to another E_Port in order to create an Inter-Switch Link (ISL) between switches. Fibre Channel Addresses Fibre Channel uses two types of addresses to identify and locate devices in a switched fab- ric: World Wide Names (WWNs) and Fibre Channel Identifiers (FCIDs). In theory, a WWN is a fixed 8-byte identifier that is unique per Fibre Channel entity. Fol- lowing the format used in Cisco Fibre Channel devices, this writing depicts WWNs as colon-separated bytes (10:00:00:00:c9:76:fd:31, for example). Technet24.ir 240 CCNA Cloud CLDFND 210-451 Official Cert Guide A Fibre Channel device can have multiple WWNs, where each address may represent a part of the device, such as: ■ Port WWN (pWWN): Singles out one interface from a Fibre Channel node (or a Fibre Channel host bus adapter [HBA] port) and characterizes an N_Port ■ Node WWN (nWWN): Represents the node (or HBA) that contains at least one port ■ Switch WWN (sWWN): Uniquely represents a Fibre Channel switch ■ Fabric WWN (fWWN): Identifies a switch Fibre Channel interface and distinguishes an StorageF_Port Area Network (SAN) Figure 8-17 displays how these different WWNs are assigned to distinct components of a Technet24.ir duplicated host connection to a Fibre Channel switch. 246 CCNA Cloud CLDFND 210-451 Official Cert Guide Switch WWN (sWWN) Server Switch1 Switch2 Port WWNs Fabric WWNs Array pWWN1 fWWN1 HBA pWWN2 fWWN2 HBA Fabric Login (FLOGI) Fabric Login (FLOGI) Server Fibre Channel Node WWN Switch (nWWN) Port Login (PLOGI) ptg17120290 WWN:Figure 8-17 World Fibre ChannelWide WorldNames Wide Names pWWNIn opposition,: Represent FCIDs are administratively N_Port assigned addresses that are inserted on Fibre Channel frame headers and represent the location of a Fibre Channel N_Port in a switched Process Login (PRLI) nWWNtopology.: AnRepresent FCID consists a of node 3 bytes, (HBA)which are detailed in Figure 8-18. Figure 8-21 Fibre Channel Logins sWWN: Uniquely representSize a Fabricin Switch Figure 8-21 also shows subsequent PLOGI and PRLI processes between the same HBA and 88 88 Bits fWWN: Uniquely represent F_Port a storage array port. After all these negotiations, both devices are ready to proceed with FCID:Domain Administratively ID Area ID Port assignedID address à Domaintheir upper-layer ID + protocolArea communicationID + Port using ID Fibre Channel frames. Figure 8-18 Fibre Channel Identifier Format Zoning ptg17120290 A zone is defined as a subset of N_Ports from a fabric that are aware of each other, but Each byte has a specific meaning in an FCID, as follows: not of devices outside the zone. Each zone member can be specified by a port on a switch, WWN, FCID, or human-readable alias (also known as FC-Alias). ■ Domain ID: Identifies the switch where this device is connected Zones are configured in Fibre Channel switched fabrics to increase network security, intro- ■ Area ID: May represent a subset of devices connected to a switch or all NL_Ports con- duce storage access control, and prevent data loss. By using zones, a SAN administrator can nected to an FL_Port avoid a scenario where multiple servers can access the same storage resource, ruining the ■ Port ID: Uniquely characterizes a device within an area or domain IDstored data for all of them. A fabric can deploy two methods of zoning: To maintain consistency with Cisco MDS 9000 and Nexus switch commands, this writing describes FCIDs as contiguous hexadecimal bytes preceded by the “0x”■ symbol Soft zoning: (0x01ab9e, Zone members are made visible to each other through name server queries. for example). With this method, unauthorized frames are capable of traversing the fabric. ■ Hard zoning: Frame permission and blockage is enforced as a hardware function on the fabric, which in turn will only forward frames among members of a zone. Cisco Fibre Channel switches only deploy this method. TIP In Cisco devices, you can also configure the switch behavior to handle traffic between unzoned members. To avoid unauthorized storage access, blocking is the recommended default behavior for N_Ports that do not belong to any zone. A zone set consists of a group of one or more zones that can be activated or deactivated with a single operation. Although a fabric can store multiple zone sets, only one can be Chapter 8: Block Storage Technologies 247 active at a time. The active zone set is present in all switches on a fabric, and only after a zone set is successfully activated can the N_Ports contained in each member zone perform PLOGIs and PRLIs between them. NOTE The Zone Server service is used to manage zones and zone sets. Implicitly, an active zone set includes all the well-known addresses from Table 8-5 in every zone. Storage Area NetworkFigure 8-22 (SAN) illustrates how zones and an active zone set can be represented in a Fibre Chan- nel fabric. Soft Zoning: Zone A ü Zone numbers are visible to each other through Name Zone C Servers ü Unauthorized frames are Zone B Zone A Zone B capable of traversing the Zone C fabric Zone Set ABC (Active) Hard Zoning: Figure 8-22Zone Zones A: andSingle Zone initiator Sets à Single Target ptg17120290 ü Only authorized frames are Although Zoneeach zone B: Multiple in Figure 8-22initiator (A, B, à andSingle C) contains Target two or three members, more hosts permitted among the could be insertedZone C: in Single them. Wheninitiator performing à Multiple a name Target service query (“dear fabric, whom can 8 members in a zone I communicate with?”), each device receives the FCID addresses from members in the same zone and begins subsequent processes, such as PLOGI and PRLI. Additionally, Figure 8-22 displays the following self-explanatory types of zones: ■ Single-initiator, single-target (Zone A) ■ Multi-initiator, single-target (Zone B) ■ Single-initiator, multi-target (Zone C) TIP Because not all members within a zone should communicate, single-initiator, single- target zones are considered best practice in Fibre Channel SANs. SAN Designs In real-world SAN designs, it is very typical to deploy two isolated physical fabrics with servers and storage devices connecting at least one N_Port to each fabric. Undoubtedly, such best practice increases storage access availability (because there are two independent paths between each server and a storage device) and bandwidth (if multipath I/O software is installed on the servers, they may use both fabrics simultaneously to access a single storage device). Technet24.ir 248 CCNA Cloud CLDFND 210-451 Official Cert Guide There are, of course, some exceptions to this practice. In many data centers, I have seen backup SANs with only one fabric being used for the connection between dedicated HBA ports in each server, tape libraries, and other backup-related devices. Another key aspect of SAN design is oversubscription , which generically defines the ratio between the maximum potential consumption of a resource and the actual resource allocat- ed in a communication system. In the specific case of Fibre Channel fabrics, oversubscrip- tion is naturally derived from the comparison between the number of HBAs and storage ports in a single fabric. Because storage ports are essentially a shared resource among multiple servers (which rarely use all available bandwidth in their HBAs), the large majority of SAN topologies are expect- ed to present some level of oversubscription. The only completely nonoversubscribed SAN 590 CCNA Data Center DCICN 200-150 Official Cert Guide topology is DAS, where every initiator HBA port has its own dedicated target port.